Yesterday, having returned from a recent trip when our Onan 2800 stopped working, I took it to our local Cummins/Onan distributor to have it repaired. During the visit, I learned two things.

In short, it was "low" on oil, thus part of the problem of why it wouldn't run. It was about 1/4 of one quart "low", and, since it only holds one quart anyway, that was enough to cause it to fail to run - the low oil safety cutoff did its job.

From the Onan "tech" the first thing I learned was that the "recommended" way (maybe his recommended way) to check the oil level in a 2800 is to NOT screw the dipstick in when checking the oil level. I.e., remove the dipstick, wipe it clean, then insert it, but don't screw it in, then remove it to check the oil level. Common sense says that using that technique will require just a skosh more oil in the sump.

The second thing I learned while waiting was that Cummins/Onan now offers a "Cummins Power Club" annual membership for $19.95 per year which entitles the member to a 10% discount on all parts and service to their Onan genset and/or Dodge pickup Cummins engine (but not for other Cummins products).

What was interesting was that, once the work was started on our genset, I stumbled upon the sales brochure, phoned the number provided on the brochure - 866.442.9576 - joined on the spot, and enjoyed the discount on yesterday's service. I saved more than the membership fee on the service ticket. You do need your genset model number and serial number to join the program. The plan is a Cummins plan, not a "dealer" plan, thus it's good nationwide.

Frankly, I never thought to "check the oil level", but, had I done so, I would have screwed the dipstick back in - as that's the way I do it on all our "yard" equipment with a similar dipstick - and I would have thought that the oil level was fine.

But, the unit is serviced, 'tis ready for next month's trip (and beyond), purrs like a kitten, and I'm a happy camper (pun intended).

FWIW, though Cummins/Onan "recommends" changing the oil every 150 hours, I usually do so around 25 hours. After all, it is an air cooled engine with no oil filter. Since the cost of a quart of oil is around $3 or $4, that's MUCH cheaper than any repair. Others may disagree, but it's just what I do. Yard equipment the same interval. In our case, it seems that when it's time to change the Chevrolet engine oil (we use Mobil 1) at about 5,000 miles, the genset clock is around 25 additional hours. If less than 25, we change it anyway. So, both are changed at the same time - different engines, different oil, but both are changed.

The screw in type dip sticks on most small engines, or all small engines that I'm aware of, are designed so that the oil is checked without screwing them in. Motorcycle engines are the same.

Another oil related issue I've come across is generators that will start, run for a few seconds, then shut down, then start again, shut down again, etc., until finally they continue running. This can be due to thick oil in cold weather. Even though the oil level is correct the thick oil is pulled up into the engine so not enough is left in the sump to satisfy the oil level sensor. Switching to a lower viscosity oil solves the problem.

I know that this isn't my forum, and I don't want to muddy the waters but it has always been my understanding that the dipstick on onan rv generators should be screwed in when checking the oil. I looked at the "Onan R.V. Generator Handbook" online and this is what I found:

Q: When I’m checking my oil, does the dipstick need to be screwed
in all the way?
A: In order to get the correct oil level reading, the dipstick must be screwed in completely on all models with a screw-type dipstick, except for the RV QG
2800/2500 & RV QG 2800/2500 RM models; it sits on top of the fill tube.
Make sure the vehicle is level when checking oil level.

Since which way it is done can mean a substantial difference in the amount of oil, it is an important point. Overfilling the crankcase can also be harmful to the engine. This answer specifically excludes the 2800 models where the stick sits on top of the fill tube. I don't know if the exclusion applies to your model or not.

Son of Norway wrote:I know that this isn't my forum, and I don't want to muddy the waters but it has always been my understanding that the dipstick on onan rv generators should be screwed in when checking the oil.

The Onan tech did say that "not screwed in" was ONLY for the 2800 (and, I'm guessing the 2500 LP as well) and that all others (larger, I presume) are to be "screwed in".

I just happen to have my Onan 2800 manual by my desk. The model is 2.8KVFA26100K. The manual definitely shows a fuel filter and an air filter. Just to confirm, don't screw the dipstick in when checking the oil.

TinyoneRV wrote:I just happen to have my Onan 2800 manual by my desk. The model is 2.8KVFA26100K. The manual definitely shows a fuel filter and an air filter. Just to confirm, don't screw the dipstick in when checking the oil.